A variety of harmful heavy metal ions are contained in some industrial waste water and must be removed by waste water treatment as much as possible in view of the prevention of environmental pollution. Since many of such heavy metal ions can be effectively used, for example, as useful metals, it serves as a double purpose to separate, recover and use them effectively as secondary resources.
Ion exchange resins have been widely used for removing harmful heavy metal ions and for capturing useful metal ions contained in, for example, water before or after use. However, the ion exchange resins cannot always have sufficient effects of selectively adsorbing metal ions at low concentration.
Chelate-forming resins capable of forming a chelate with metal ions to thereby selectively capture these metal ions have excellent capability of selectively capturing metal ions, especially of capturing heavy metal ions, thus the chelate resins are used to remove or capture heavy metals in the field of water treatment.
However, since most of the chelate-forming resins are bead-like resins having a rigid three-dimensional crosslinked structure formed by action of a crosslinking agent such as divinylbenzene and are hydrophobic, a rate of diffusion of metal ions or regenerants into the resins is slow. Thus, treatment efficiency is insufficient. In addition, in the disposal type of the resins without being regenerated, since it is difficult to subject the used resins to the incinerating disposal, problems such as volume reduction of the used resins have been greatly pointed out.
As a possible solution to these problems of bead-like chelatable resins, a fibrous chelate-forming resin has been proposed (Japanese Patent No. 2,772,010). The fibrous chelate-forming resin has a large specific surface area, includes a metal chelate-forming functional group, where metal ions are adsorbed or desorbed, on its surface, and therefore has an improved adsorption and desorption capability.
However, the process for producing the fibrous chelate-forming resin, namely modification to impart metal chelating activity to the resin, Is complicated and requires a special process using, for example, ionizing radiation, and a number of disadvantages have been pointed out in terms of, for example, facilities, safety, and production cost.